Pontoon Boat & Deck Boat Forum

Hello all! Just wondering if anyone else may have had the problem I am having. I bought a new Bentley 20' pontoon about 2 months ago. It is rigged with a Honda 90 four stroke. My problem is ventilation or cavitation I really don't know how to tell the difference between the two. It came with a 15 pitch prop, talked with the manufacturer and they recommend a 13 pitch. The 13 got my rpm up to 6000 wide open. But still blowing out even with all passengers in the rear of the boat. I can be running along the lake calm water and all of a sudden it is like hitting a patch of ice. Any ideas?

If the dealer did the rigging, they may have set the motor too high. Have you taken someone from the dealership on a ride to show them what happens?
There have been threads that talk about where the motor should be mounted, how much of the lower unit is in the water, etc., but I would think the dealer at least test drove it to make sure the problem you described wasn't happening. But then again maybe not.
Talk to the dealer.

It is mounted as low as possible on the transom. Trimmed all the way down. If I even try trimming it up to blows out immediately.

SteveCoates wrote:It is mounted as low as possible on the transom. Trimmed all the way down. If I even try trimming it up to blows out immediately.

That sounds too low. You're going to bring it up higher the transom. There are several good posts with pictures that will help you understand what the optimal height is.

My old 24' Starcraft pontoon ventilates every time too many people sit in the front end. Front end weight lifts the engine slightly, and just a little lift makes a difference. I have to ask people to move to the rear.

My 20" Yamaha 115 hp 2 stroke motor was taken off a bassboat (in trade), and a 25" motor would have worked better on my given hull.

Your motor probably needs lowered on the transom, or the transom refabricated. Easiest way would be to get a manual adjustable jack plate, and do some experimenting with engine heights. And, sometimes another propeller can make a difference. But a 90 hp on a 20' boat should perform well with a 15 pitch prop.

See what your dealer's willing to do about it. He surely doesn't want any unhappy customers. In my eyes, it's a dealer's responsibility to adjust the engine and put the correct prop on it for total performance.

Thanks for input !